Neural generators of early cortical somatosensory evoked potentials in the awake monkey

Nancy Nicholson Peterson, Charles E. Schroeder, Joseph C. Arezzo

Research output: Contribution to journalArticlepeer-review

128 Scopus citations


Controversy continues to exist regarding the generators of the initial cortical components of the somatosensory evoked potential (SEP). This issue was explored by detailed epidural and intracortical mapping of somatosensory evoked activity in Old World monkeys. In depth recordings, 3 complementary procedures were utilized: (1) the intracortical and subcortical distribution of SEPs was determined from approximately 4000 locations; (2) concomitant profiles of multiple unit activity (MUA) were recorded as an estimate of local action potential profiles; (3) 1-dimensional calculations of current source density (CSD) were used to outline the timing and pattern of regional transmembrane current flow. Our analysis confirms the participation of multiple cortical areas, located on either side of the central sulcus, in the generation of the initial cortical SEP components. Earliest activity, P10, was localized to area 3, followed within milliseconds by activation of areas 1, 2 (P12), and 4 (P13). In SI (Brodmann's areas 3, 1 and 2), the initial SEP components reflect the depolarization of lamina 4 stellate cells and the subsequent activation of adjacent pyramidal cells in laminae 3 and 5. The genesis of later cortical components (P20, N45) represents the composite of activity distributed across multiple cortical laminae and the interaction of overlapping excitatory and inhibitory events. These findings have direct implications for the clinical interpretation of SEP waveforms.

Original languageEnglish (US)
Pages (from-to)248-260
Number of pages13
JournalElectroencephalography and Clinical Neurophysiology/ Evoked Potentials
Issue number3
StatePublished - May 1995


  • (Monkey)
  • Cortex
  • Current source density
  • Evoked potentials
  • Somatosensory evoked potentials

ASJC Scopus subject areas

  • Neuroscience(all)
  • Clinical Neurology


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